JFrame bugando com Thread

Programação
#1

Eu to desenvolvendo um programa em que depois que eu logar, ele vai aparecer um novo JFrame com um JProgressBar para carregar outro JFrame, porem quando eu faço isso usando Threads, o JFrame com o JProgressBar so aparece quando a janela que era pra ser carregada aparecer

public class AberturaUsuario extends javax.swing.JFrame {
       public void barraLoading(){
            Aluguel c1 = new Aluguel();
            try{
            for(int i=1;i<=100;i+=1){
            
            loading.setValue(i);
            loading.setString(i+"%");
            Thread.sleep(30);
            
            }
            //O problema parece estar nesses Threads
            Thread.sleep(1000);
            setVisible(false);
            Thread.sleep(1000);
            c1.setVisible(true);
            
            }
            catch(InterruptedException a){
            
            a.printStackTrace();
            
            }}
        
        
        
        public AberturaUsuario() {
            initComponents();
            setVisible(true);
            barraLoading();
        }

        @SuppressWarnings("unchecked")
        // <editor-fold defaultstate="collapsed" desc="Generated Code">                          
        private void initComponents() {

            kGradientPanel1 = new keeptoo.KGradientPanel();
            jLabel1 = new javax.swing.JLabel();
            jLabel3 = new javax.swing.JLabel();
            loading = new javax.swing.JProgressBar();

            setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
            setUndecorated(true);

            kGradientPanel1.setkEndColor(new java.awt.Color(7, 117, 0));
            kGradientPanel1.setkStartColor(new java.awt.Color(53, 223, 36));

            jLabel1.setFont(new java.awt.Font("Gabriola", 0, 78)); // NOI18N
            jLabel1.setText("Biblioteca Virtual");

            jLabel3.setIcon(new javax.swing.ImageIcon(getClass().getResource("/Imagens/iconeAluno.png"))); // NOI18N

            loading.setForeground(new java.awt.Color(218, 0, 0));

            javax.swing.GroupLayout kGradientPanel1Layout = new javax.swing.GroupLayout(kGradientPanel1);
            kGradientPanel1.setLayout(kGradientPanel1Layout);
            kGradientPanel1Layout.setHorizontalGroup(
                kGradientPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, kGradientPanel1Layout.createSequentialGroup()
                    .addGap(62, 62, 62)
                    .addComponent(jLabel3, javax.swing.GroupLayout.PREFERRED_SIZE, 127, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                    .addGroup(kGradientPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                        .addComponent(loading, javax.swing.GroupLayout.PREFERRED_SIZE, 410, javax.swing.GroupLayout.PREFERRED_SIZE)
                        .addComponent(jLabel1))
                    .addGap(163, 163, 163))
            );
            kGradientPanel1Layout.setVerticalGroup(
                kGradientPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                .addGroup(kGradientPanel1Layout.createSequentialGroup()
                    .addGroup(kGradientPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                        .addGroup(kGradientPanel1Layout.createSequentialGroup()
                            .addGap(55, 55, 55)
                            .addComponent(jLabel3)
                            .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, 29, Short.MAX_VALUE))
                        .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, kGradientPanel1Layout.createSequentialGroup()
                            .addContainerGap(javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                            .addComponent(jLabel1, javax.swing.GroupLayout.PREFERRED_SIZE, 59, javax.swing.GroupLayout.PREFERRED_SIZE)
                            .addGap(61, 61, 61)))
                    .addComponent(loading, javax.swing.GroupLayout.PREFERRED_SIZE, 24, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addGap(83, 83, 83))
            );

            javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
            getContentPane().setLayout(layout);
            layout.setHorizontalGroup(
                layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                .addComponent(kGradientPanel1, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
            );
            layout.setVerticalGroup(
                layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                .addComponent(kGradientPanel1, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
            );

            pack();
            setLocationRelativeTo(null);
        }// </editor-fold>                        
        public static void main(String args[]) {
                    new AberturaUsuario();
        }
#2

Não achei o uso de threads no seu código. Veja um exemplo:

Thread t1 = new Thread(new Runnable() {
	@Override
	public void run() {
		// Faz algo
	}
});

t1.start();
#3

Você não criou Thread nenhum, você só está pausando a execução da Thread atual, que corresponde a execução de seu programa.

Se você quer executar o método barraLoading concorrentemente com as Threads do Swing, chame o método barraLoading dessaforma:

SwingUtilities.invokeLater(() -> barraLoading());
#4

Parece que o problema não é esse, quando eu seto em uma classe para tornar o AberturaUsuario visivel, ele tem que esperar a função barraLoading carregar para so então aparecer,mas quando instancio para ser a classe visivel dentro dessa função, ele ainda permanecer invisivel ate acabar de carregar a barra de loading