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  • java常用代码

    1、List遍历

    List<String> items = new ArrayList<>();
    items.add("A");
    items.add("B");
    items.add("C");
    items.add("D");
    items.add("E");
    
    //lambda
    //Output : A,B,C,D,E
    items.forEach(item->System.out.println(item));
        
    //Output : C
    items.forEach(item->{
        if("C".equals(item)){
            System.out.println(item);
        }
    });
        
    //method reference
    //Output : A,B,C,D,E
    items.forEach(System.out::println);
    
    //Stream and filter
    //Output : B
    items.stream()
        .filter(s->s.contains("B"))
        .forEach(System.out::println);

    2、Map遍历

    Map<String, Integer> items = new HashMap<>();
    items.put("A", 10);
    items.put("B", 20);
    items.put("C", 30);
    items.put("D", 40);
    items.put("E", 50);
    items.put("F", 60);
    
    items.forEach((k,v)->System.out.println("Item : " + k + " Count : " + v));
    
    items.forEach((k,v)->{
        System.out.println("Item : " + k + " Count : " + v);
        if("E".equals(k)){
            System.out.println("Hello E");
        }
    });

     3、遍历enum

    public enum ColumnTypeEnums {
        INTEGER("int", "Integer"),
        VARCHAR("varchar", "String"),
        DATE("date", "java.util.Date"),
        TIME("datetime", "java.util.Date"),
    
        NUMERIC("numeric", "java.math.BigDecimal"),
        DECIMAL("decimal", "java.math.BigDecimal"),
        TINYINT("tinyint", "byte"),
        SMALLINT("smallint", "short"),
        BIGINT("bigint", "long"),
        FLOAT("float", "double"),
        DOUBLE("double", "double"),
        CHAR("char", "String");
    
        private String pdm;
        private String java;
    
        public void setPdm(String pdm) {
            this.pdm = pdm;
        }
    
        public void setJava(String java) {
            this.java = java;
        }
    
        public static ColumnTypeEnums getByPdm(String pdm) {
            ColumnTypeEnums e = null;
            for (ColumnTypeEnums en : ColumnTypeEnums.values()) {
                if (en.getPdm().equals(pdm)) {
                    e = en;
                }
            }
            return e;
        }
    
        public static void main(String[] args) {
            ColumnTypeEnums e = ColumnTypeEnums.getByPdm("tinyint");
            Console.log("===============");
            Console.log("{},{},{}", e.name(), e.getPdm(), e.getJava());
        }
    }
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  • 原文地址:https://www.cnblogs.com/yaoyuan2/p/10578681.html
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